Minoxidil (topical)

Topical minoxidil is the longest-running standard treatment for androgenetic alopecia, FDA-approved over-the-counter since 1988 (2% solution) and 1997 (5% solution).¹ The 5% formulation — available as solution or foam — is the standard for men today.

How it works

Minoxidil is a vasodilator and potassium-channel opener. Applied to the scalp, it appears to extend the anagen (growth) phase of the hair cycle, increase follicle size, and improve scalp microcirculation around the follicle.² The active form is minoxidil sulfate, produced when sulfotransferase enzymes in scalp tissue convert minoxidil to its active metabolite — which is one reason individual response varies. Patients with low sulfotransferase activity respond less to topical minoxidil.³

What the evidence supports

Robust randomized data shows 5% topical minoxidil produces meaningful hair-count improvements in the majority of men with androgenetic alopecia, with the strongest effect on vertex thinning.⁴ Onset is gradual — the typical pattern is mild shedding in weeks 2–8 as the hair cycle resets, followed by visible thickening by month 4–6 and continued improvement through month 12. Stopping reverses the gains over 3–6 months.

Foam vs solution

• Foam is generally preferred: faster-drying, no propylene glycol (the main irritant in solution), and less likely to drip onto the forehead.
• Solution remains an option for men who prefer it or who find foam difficult to apply over longer hair.
• Both are 5% strength; head-to-head data shows comparable efficacy.

Combining with other treatments

Topical minoxidil pairs well with oral or topical finasteride — different mechanisms, additive effect. Combination is the standard recommendation for serious androgenetic alopecia.⁵ Patients who plateau on topical-only often benefit from adding finasteride or transitioning to low-dose oral minoxidil.